For recovery of solvent vapor from the drying of articles with the help of an air stream, a closed system of pipes guide the air stream through a heat exchanger comprising a condenser and an air heater. This system of pipes has a blower for circulation of the air flow and a switching means comprising a plurality of valves and at least one pipe segment by which a solvent adsorber is connectable in series in the circulation with the article-processing vessel.
In the dry cleaning apparatus described in German Pat. No. 22 14 153, for example, the drying of the articles is effected with recovery of the solvent vapor from the air stream in a first stage by condensation of the solvent followed by heating the air flow recycled passing over the goods.
A recovery by adsorption instead of condensation is not practiced in an early stage, since the solvent-vapor concentration at the start of the drying is much too high for an adsorption process. Therefore, in the known apparatus during the drying by condensation, the adsorber which contains active carbon as an adsorbing material is shunted by a bypass. Then toward the end of the drying, when the gas concentration has been reduced to a small value, the adsorber is switched into the circulation.
In this known arrangement, the adsorber is located upstream of the processing container and downstream of the outlet of the heater. It is thus acted upon by the heat picked up by the air flow from the heater. As a consequence, the adsorption capacity of the adsorber is greatly diminished inasmuch as adsorption capacity of an active carbon adsorbent declines with rising temperature. This phenomenon is noted even when the heater is switched off since substantial heat is retained by the heater and hence is transferred to the air stream traversing the heater.
As a result, up to now a correspondingly large amount of active carbon has been required as an adsorption agent for sufficient adsorption to occur in the solvent cleaning industry under these conditions. The adsorber, because of the volume of adsorbent required, cannot be put in the machine housing, but must be placed instead outside of it.
Furthermore, this adsorber requires correspondingly large devices and periodic effort for desorption which may require the use of steam or hot gas. Because of the various cycle times for the desorption cycle and drying times with large-volume adsorbers it is generally necessary to use a twin adsorber with individual heat exchangers and also a comparatively large carbon capacity and to alternate between the adsorbers, desorbing one while the other is operating in an adsorption mode.